Abstract
BackgroundTrachoma is a major cause of blindness in Southern Sudan. Its distribution has only been partially established and many communities in need of intervention have therefore not been identified or targeted. The present study aimed to develop a tool to improve targeting of survey and control activities.Methods/Principal FindingsA national trachoma risk map was developed using Bayesian geostatistics models, incorporating trachoma prevalence data from 112 geo-referenced communities surveyed between 2001 and 2009. Logistic regression models were developed using active trachoma (trachomatous inflammation follicular and/or trachomatous inflammation intense) in 6345 children aged 1–9 years as the outcome, and incorporating fixed effects for age, long-term average rainfall (interpolated from weather station data) and land cover (i.e. vegetation type, derived from satellite remote sensing), as well as geostatistical random effects describing spatial clustering of trachoma. The model predicted the west of the country to be at no or low trachoma risk. Trachoma clusters in the central, northern and eastern areas had a radius of 8 km after accounting for the fixed effects.ConclusionIn Southern Sudan, large-scale spatial variation in the risk of active trachoma infection is associated with aridity. Spatial prediction has identified likely high-risk areas to be prioritized for more data collection, potentially to be followed by intervention.
Highlights
Trachoma, caused by the bacterium Chlamydia trachomatis, is the most common infectious cause of blindness and the leading cause of preventable blindness worldwide [1,2]
In Southern Sudan, large-scale spatial variation in the risk of active trachoma infection is associated with aridity
Recent surveys have found both extremely high prevalence of active trachoma (trachomatous inflammation-follicular (TF) and/or trachomatous inflammationintense (TI)) and evidence of Trachomatous trichiasis (TT) in children in some of the areas surveyed [25,26]. These findings indicate that trachoma constitutes a major problem to public health in Southern Sudan [27]
Summary
Trachoma, caused by the bacterium Chlamydia trachomatis, is the most common infectious cause of blindness and the leading cause of preventable blindness worldwide [1,2]. Repeated infection with C. trachomatis leads to scarring of the conjunctiva and eventually entropion, causing the lashes of the inwardly-turned eyelid to abrade the corneal surface, a condition referred to as trichiasis [3,4]. Unless eyelid deformation is managed surgically, trichiasis causes irreversible scarring of the cornea leading to corneal opacity and, eventually, blindness. Prevention is partly based on improving personal hygiene by promoting facial cleanliness and providing clean water for face washing, and promoting the safe disposal of human faeces, thereby reducing fly abundance [9]. Facial cleanliness and Environmental improvement form two of the four components of the World Health Organization (WHO) recommended ‘‘SAFE’’ strategy for trachoma control, which includes Surgical correction of trichiasis and mass drug administration (MDA) of Antibiotics in endemic communities [10]. The present study aimed to develop a tool to improve targeting of survey and control activities
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